P03 COMBINING SKY92 GENE EXPRESSION PROFILING AND IGH CLONALITY TO EVALUATE GENETIC RISK IN IRISH MULTIPLE MYELOMA PATIENTS
Authors: R McAvera, I Drozdz, H Black, T Cichocka, E Szegezdi, J Quinn, P Murphy, P Thornton, M Perera, R Clifford, N Keane, V Mykytiv, E Elhassadi, R Cummins, M O’Dwyer, S Glavey
Journal: HemaSphere (2023)

Multiple myeloma (MM) is an incurable malignancy characterised by clonal proliferation of malignant plasma cells in bone marrow (BM). Currently, there are a lack of standardised approaches to determine patient prognosis and response to therapy. The MMProfiler is a prognostic test based on the well validated SKY92 gene signature which can accurately identify high-risk (HR) patients at diagnosis with survival of less than 2 years. The achievement of minimal residual disease (MRD) negativity after therapy is considered a key goal of treatment. Recent evidence indicates that achievement of MRD negativity may improve the PFS of MM patients with HR cytogenetics but data supporting this in SKY92-defined HR are lacking. NGS approaches have aimed to standardise MRD testing by monitoring clonal, disease-driving IGH rearrangements. Through an ongoing national study, for the first time in Ireland we are combining two genomic approaches with the aim of improving baseline genetic risk-stratification as well as subsequent assessment of response to treatment based on MRD. Ultimately, we aim to determine how SKY92 risk impacts the ability to achieve MRD negativity in transplant eligible (TE) patients. Diagnostic and follow-up BM samples were provided from TE MM patients across Ireland. Both a mononuclear cell (MNC) fraction and CD138+ fraction were isolated using SepMate tubes and the EasySep CD138+ selection kit respectively. Briefly, RNA from CD138+ plasma cells at diagnosis was used for SKY92 classification using MMProfiler (Affymetrix arrays). Invivoscribe LymphoTrack PCR-based IGH-FR1 assay and sequencing using the Illumina MiSeq platform were used to identify clonal DNA rearrangements at diagnosis. Clonality is defined as ≥2.5% of the total reads of that sample and greater than two times the third-ranked top sequence. This clonal sequence identified will be used for MRD monitoring using DNA from MNCs post-ASCT. Preliminary results show that 11/33 (33.3%) patients were classified as SKY92 HR. In addition, t(4;14) was detected in 27.2% patients, t(11;14) in 12.1%, t(14;16)/t(14;20) in 6.1% and gain(1q) in 45.5%. There was an association between SKY92 HR signature and t(4;14) (63% HR vs 9.1% SR, p<0.01), and a higher proportion also had gain(1q) (63.6% HR vs 36.4% SR). Both t(4;14) and gain(1q) are often considered as independent HR markers. Interestingly, the prevalence of SR cytogenetic marker t(11;14) was similar (9.1% HR vs 13.6% SR). LymphoTrack IGH-FR1 assay detected clonality in 16/19 patients (84.2%). Remaining patients will be sequenced using additional LymphoTrack IGH assays until a clonal sequence is determined. At follow-up, we will determine if these clonal sequences remain present post-ASCT using the appropriate targeted assay. Optimisation of DNA input and sequencing depth will define the sensitivity of MRD negativity. We successfully identified clonal IGH rearrangements in the majority of newly diagnosed MM patients, and expect this to reach >95% in combination with additional IGH-targeting assays. These clonal sequences will be used to monitor MRD. A significant proportion of MM patients in Ireland present with HR disease as defined by both SKY92 and cytogenetic profile. Future work will aim to evaluate the achievement of MRD negativity based on SKY92 status, and whether this impacts survival. We will continue to profile Irish patients and ultimately, we hope this could lead to a more risk-stratified treatment approach.